1. Field of the Invention
The present invention relates to ink jet printheads for ink jet printers, more specifically, to ink jet refill cartridges that are insertable into ink jet printheads.
2. Description of Related Art
Ink jet cartridges such as those used in ink jet printers, facsimiles, postal meters and other recording devices are generally well known in the art. These ink jet cartridges are generally comprised of a printhead, print circuitry and an integral ink container containing liquid ink to be supplied to the printhead. During printing, ink is expelled from the printhead through various ejection methods. The ink reservoir is drained during this process and eventually emptied. The structural components of the ink cartridge are durable and will last for numerous charges of ink. A substantial cost involved in the use of ink jet printers is the replacement of cartridges; over the life of the printer this cost is often two or three times the cost of the printer itself. Discarding the entire cartridge after the reservoir is emptied once is an expensive and wasteful practice.
As a result of the high cost and waste involved in disposing a fully functional, empty cartridge, many users refill ink cartridge reservoirs. Techniques have been developed to replenish ink reservoirs several times, dramatically extending the life of the cartridge.
There are several known methods and apparati for refilling the reservoirs. These methods require four main steps to refill a cartridge: fill hole access, refilling, fill hole sealing, and priming. All of the steps of the refill process present the risk of an messy ink spill. Various apparati are employed to assist in performing the four main refilling steps.
Aside from requiring a four-step process, all current methods for refilling ink reservoirs require a certain level of skill to accomplish successfully. As a result, these methods are often messy and may not yield a properly functioning cartridge. Consequently, the widespread acceptance of refilling ink jet cartridges has been limited.
Rather than inconvenience consumers with the risk of a mess, a new generation of refillable cartridges has been developed. This new generation is based on the refill manufacturer purchasing an ink jet cartridge with an integrated ink reservoir, such as the Hewlett-Packard 51633A Ink Jet Cartridge, and hollowing out the ink reservoir. The shell of the cartridge, containing the printhead and print circuitry for receiving electrical signals from a printer, may than be used to receive an ink reservoir adapted to fit therein.
These known systems have limitations. In addition, a replaceable reservoir must fit into the amount of space occupied by the original integrated reservoir. The resulting decrease in volume translates to a decrease in reservoir ink capacity. This results in environmental cost savings not being realized until the reservoir has been replaced several times.
The ink containment system can also detract from the volume of the reservoir. At least two of the systems known in the art employ reservoirs which are completely filled with a sponge. The sponge limits ink from freely flowing out of the coupling hole in the bottom of the reservoir, however, it occupies space, representing a severe limitation on the amount of ink that may be contained.
One of the reservoirs known in the art uses a design which is part sponge and part cavity. This yields the advantages of a sponge near the ink egress aperture, yet allows more ink to be contained. However, the reservoir described uses a relatively costly reservoir design having internal parts. For example, the air vent used to equalize pressure within the housing is located in the top portion of the primer bulb. Since there is a large quantity of free ink in the reservoir, a sophisticated system must be employed to prevent ink from coming out of the housing when the bulb is depressed. To obviate this problem, the device incorporates a second sponge (in addition to the sponge located over the ink egress aperture) through which air must first pass before reaching the interior of the housing. This additional sponge is positioned on the opposite side of the housing from the sponge covering the ink egress aperture and is connected by a tube to the air vent in the primer bulb. When saturated with ink, the additional sponge prevents the ink from leaking out of the housing when the primer bulb is depressed.
At least one of the known systems employs an electrical sensor to detect when the reservoir is low on ink. This increases manufacturing costs, as electrical contacts must be placed inside the cartridge housing and also contained within the reservoir. Another known system uses a priming button instead of electrical sensors. The priming button allows the reservoir to be used until completely empty, however, the spring-activated button is an additional part which increases assembly time and cost. One system known in the art has a priming circle integrated onto the reservoir as a thin, circular indentation on the wall of the reservoir. This is an optimal design, however, the priming circle has a hole, requiring an air filter within the reservoir to prevent ink from being sucked out of the reservoir after priming. The use of the filter displaces volume, and, as a result, approximately one-quarter less ink is held in the reservoir than in the original cartridge.
The ink reservoir must also be coupled to the cartridge housing. All of the known ink reservoirs contain a aperture to allow a flange in the cartridge housing to forcibly extend into the aperture. This allows ink to flow between the reservoir and the printhead. While the reservoir sponge prevents most ink leakage, some ink can still leak from the reservoir into the housing when the reservoir is inserted or removed, or if air is forced into the reservoir via a priming process. The known systems also use various attachment means to hold the reservoir to the housing.
Yet another device known in the art is the Canon BJ Cartridge BC-02. This device is a single cartridge comprised of two chambers separated by a partition wall through which the ink may pass. The first chamber is an free-ink filled chamber that does not have a sponge member contained therein. The second chamber holds a sponge that occupies the entire volume of the chamber. The ink aperture that is connected to printhead and the air vent opening are positioned on a side wall of the cartridge when in the operating position. While this device does have a reasonable storage capacity for ink, maximization of the ink storage is limited because the sponge occupies the entire volume of the second chamber. Thus, there is a substantial amount of potential ink storage capacity that is wasted in this particular device.
In another version of Canon's cartridge, there is no first free-ink chamber but a single sponge filled chamber, which, of course, has the same problems related to the other above-discussed prior art devices.
Therefore, it can readily be seen that there is a need in the art for a refill insert that is simply designed and provides for a larger capacity of ink but is less costly to manufacture. Accordingly, the present invention provides a refill insert that addresses these deficiencies.